Add Webpacker

[mberlanda]

Add Webpacker to use the JavaScript pre-processor and bundler webpack 3.
The change is the logical evolution #2 Add YARN for NodeJS assets.

Changelog

• added webpacker gem to Gemfile
• ran bundle exec rake webpack:install
• ran bundle exec rake webpack:install:react for a the next step of the application refactoring
• refactoring of application vendor stylesheets
• refactoring of application vendor javascripts

(Solved) Issues

Refactoring of application vendor assets

The first step after including yarn has been

# config/initializers/assets.rb
Rails.application.config.assets.paths << Rails.root.join('node_modules')

This implied some issues:

• SO-48572272 Rails asset pipeline working with fonts and yarn
• SO-48653276 After adding yarn and webpacker several errors in precompilation

In the answers to these questions I documented how I solved all the problems